1. Technical Field of the Invention
The invention relates in general to performance analysis of a circuit switched mobile telecommunications network. In particular, and not by way of limitation, the present invention is directed to large-scale performance analysis of 3G-324M-based Video Telephony and circuit switched streaming.
2. Description of Related Art
When introducing Video Telephony in to the Third Generation (3G) systems, instead of embracing “next generation” Internet Protocol (IP) for conversational multimedia, the high Quality of Service (QoS) and mature signaling of “old generation” Time Division Multiplexing (TDM) are used and a circuit switched communication channel is established between mobile peers. The Third Generation Partnership Program (3GPP) standard body is responsible for the Universal Mobile Telecommunications System Wideband Code-Division Multiple Access (UMTS/WCDMA) specifications. 3GPP defined specifically the structure and implementation requirements of circuit switched Video Telephony in the 3G-324M standard.
The 3GPP2 standard body, responsible for CDMA2000 specifications, in August 2002 approved a similar technical specification for 3G-324M operation requirements over CDMA2000 networks—named “3GPP2 C.S0042 for circuit switched Video Conferencing Services.”
3G-324M is currently in operation in a number of live UMTS/WCDMA networks, e.g., 3G networks operated by companies J-Phone and NTT DoCoMo in Japan.
3G-324M is a derivative of standard H.324, which is an ITU-T Recommendation of Terminal 1 for low bit rate multimedia communication, and was developed for an analog public network connection, and for V.34 modems. As a baseline of the terminal specification, standard H.324M was adopted as a mobile extension, with bit error handling procedures to support the delivery of delay-sensitive applications, e.g. video streaming and videoconferencing, over 3G networks. The protocol does not handle addressing but comes into play only after a call setup using Integrated Services User Part (ISUP) logical procedure and addressing methods according to standard E.164 over underlying 3G wireless protocol, e.g. WCDMA. In that stage the called peer is located and the call is set up between the two call peers, establishing a circuit switched channel between them. When that circuit switched channel is operating, the 3G-324M is initiated to synchronize the multiplexing-demultiplexing operation between parties and to start the call control operation according to standard H.245, which is an ITU-T Recommendation of control protocol for multimedia communication.
In FIG. 1 a possible embodiment of a 3G network is shown, a part of which belongs to circuit switched domain 101, while the other part belongs to packet switched domain 102. The network includes mobile terminals 103, 104, 105 using the 3G-324M protocols for real-time multimedia delivery; H.324 terminals 110 and H.320 terminals 111 connected to a sub-network 107 of delay-sensitive applications like video or voice transmission; and video streaming and Content Servers 112, Common Internet Applications 113 and H.323/SIP terminals 114 connected to another sub-network 108 of delay-tolerant applications like e-mail or web. A gateway 109 is applied to connect the two domains 101, 102, and a base station system 106 to establish radio link 115 among the sub-networks 107, 108 and the mobile terminals 103, 104, 105.
Another scenario, where 3G-324M is used is circuit switched streaming illustrated in FIG. 2. In this scenario, the mobile terminal 201, e.g. 3G videophone is connected to a Video Gateway 205 through radio link 115, base station system 106 and an access network 204 using 3G-324M. The Video Gateway 205 communicates with a content server 207 using the packet switched streaming solution over the packet switched core network 206. In this solution, the streaming contents are addressed through E.164 numbers dialed from the mobile terminal 201. The user dials a service number, watches the content, and hangs up when finished. The control of the video playing is supported using Dual Tone Multiple Frequency (DTMF): for example rewind 5 sec for each press on a key, pause/play, forward 5 sec for each press on a key. Typically no transcoding of video and audio codecs is performed in the Video Gateway. Audio and video codecs according to standards AMR, H.263 and MPEG-4 are supported end-to-end.
In order to be sure that a terminal is interoperable with another one, a reference terminal is needed that can be used for conformance testing purposes. This interoperability testing capability was the primary goal when the Dilithium Networks Analyzer (DNA)(Dilithium Networks Analyzer, DNW-DNA Version 2.2, LIT # 0703v3.9) was developed.
Besides Interoperability testing, this terminal is good for performance analysis, because it behaves as ordinary terminal, but also makes certain measurements on different levels of the protocol stack.
The non-intrusive network traffic monitoring option of this tool provides facilities for monitoring 3G-324M network traffic in an OFF-LINE or ON-LINE fashion. For example, it can monitor the 3G-324M data from the two end-points engaged in a call. The two end-points may be either handsets or a combination of a handset and a multimedia gateway. Applications are interoperability testing, troubleshooting, and service optimization.
In the OFF-LINE mode, DNA can be use to passively capture the data to a file. The DNA can then be used to play these data to inspect the command and control channel, and display video and play audio channels. In the ON-LINE mode, DNA (with the option) can be configured to passively monitor and intercept H.324M/3G-324M bit-streams on the bearer channel, decode the bit-stream, inspect the command and control channel, and to visualize and listen to the video and voice channels. The quality of the service can be inspected in terms of video and voice bit-rates, video frame-rate, and the error rate from the multiplexer. The voice and video data can be saved to file and further analysis of the data using more specialized voice and video analysis tools can be performed if needed.
Besides the above mentioned analyzer tool, there are certain performance counters implemented in network nodes, which can be used to trace performance problems. These counters are not dedicated for specific services, but rather for the UMTS system.
The existing solutions such as DNA, cannot be used to answer certain questions, which arise at network operators: E.g. To what extent is my network used for Video Telephony? Or: What are the characteristics of the call traffic? Or: How many calls could not be set up and why? Or: Was the quality of the successful calls satisfactory? In other words, there exists no tool for analyzing large amount of videophone traffic, and therefore statistical measures on the usage and quality of the service in a live network is rather difficult to determine convincingly.
There are several problems with the counters as well: The counters are typically not service-specific, but system specific devices. It means that service-specific statistical data cannot be obtained. Counters do not work on all protocol elements. For example in case of Video Telephony the analysis should involve a lot of control plane signaling protocols, and the different logical channels within the H.223 multiplex, where H.223 protocol is a ITU-T Recommendation of multiplexing protocol for low bit rate multimedia communication. To obtain certain measures all of these protocol levels are needed, for example the time between call initiation and the time when the first video frame arrives. Moreover, different vendors implement different counters, and it makes it impossible to build a coherent performance monitoring system in a multivendor network. Finally, the node resources for this purpose are limited. In general, significant hardware/software resources are needed for measuring Key Performance Indicators, which can increase the costs of network elements. A further consequence of the fact that the resources available for counter-based performance analysis are limited is that the time resolution of these counters is coarse.
We have set ourselves the objective with this invention to improve the solutions described above by implementing a performance analysis of a circuit switched mobile telecommunications network especially for large-scale measurement of 3G-324M Video Telephony and circuit switched streaming.